Last Sunday morning I went to Wisley again on my way to Kent. This is the state of play in the Grow Your Own Veg 3 x 3 plot.
The third picture shows the diagram they suggested they were following earlier in the year. You will see that there is no mention of sweetcorn on there, but there is some in the beds.
It really does demonstrate that the 3 x 3 system does provide a variety of veg and herbs throughout the summer and autumn. Very worthwhile for someone with only a little space to garden.